A conventional cover apparatus in this kind of battery is such that a top wall of a cover thereof is formed with holes which are in communication with respective cell chambers, and a grooved frame body a channel shape in section is fixed to the outer surface thereof by an adhesive agent or by heat melting adhesion or the like to form an exhaust passage common to these cell chambers, and consequently the same has such inconveniences that there is such a fear that the fixed portion thereof peels off or electrolyte in the interior thereof leaks out to the outer surface of the cover through that portion, and that the same is deteriorated in appearance by the fixed portion.